Saris wrote in her opinion that the Medicare system created perverse incentives by pegging reimbursement for drug transactions to a price reported by the drug industry without any oversight. Other insurers also use the system, since abandoned by Medicare.

Pharmaceutical companies took advantage of the system by “establishing secret mega-spreads between the fictitious reimbursement price they reported and the actual acquisition costs of doctors and pharmacies,” she wrote.

Saris decided a portion of the case dealing with Massachusetts law. The decision makes it likely she will certify a class action for claims from other states, the newspaper says.